THE EFFECTS OF STRYCHNINE AND CAFFEINE 

 UPON THE RATE OF LEARNING 



K. S. LASHLEY 

 Department of Psychology of the Johns Hopkins University 



Among the hypotheses which have been advanced to account 

 for the reintegration of conduction paths in learning three stand 

 out as rather definitely opposed to one another in the neural 

 processes which they imply. The hypothesis suggested by 

 Ladd and Woodworth ('11) assumes inhibition of successive 

 activities as the fundamental process which results in the selec- 

 tion and fixation of random activities. The second hypothesis 

 assumes nervous reinforcement as the fundamental process by 

 which successive acts become linked together in habit-formation. 

 In its vaguest forms this hypothesis refers to pleasure and pain 

 as the reinforcing agents without any attempt to analyze the 

 way in which they act. Its most concrete expression is that 

 given by Angell ('09), though the diagram which he gives has 

 little correspondence with physiological facts. The third hy- 

 pothesis depends chiefly upon the chance spreading of nervous 

 excitation (Watson, '14 a), or the simultaneous activation of 

 two afferent pathways in such a way that the final common 

 path of one is able to divert the discharge of the other and so 

 bring about a permanent connection between itself and this 

 afferent path (Max Meyer, '11), (Pawlow, '14). If Sherrington's 

 explanation of the spreading of nerve impulses as a result of 

 fatigue of the final common path be accepted, the mechanism 

 implied in this hypothesis is relatively independent of inhibi- 

 tory and reinforcing activities of the nervous system. 



The studies of Verworn and of Sherrington have shown 

 that the primary action of strychnine upon the central nervous 

 system is the reduction of inhibitory processes and their final 

 conversion into processes of excitation. A means is thus pro- 



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